using System;

using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.X509;

namespace Org.BouncyCastle.Asn1.Ocsp
{
	public class Signature
		: Asn1Encodable
	{
		internal AlgorithmIdentifier	signatureAlgorithm;
		internal DerBitString			signatureValue;
		internal Asn1Sequence			certs;

		public static Signature GetInstance(
			Asn1TaggedObject	obj,
			bool				explicitly)
		{
			return GetInstance(Asn1Sequence.GetInstance(obj, explicitly));
		}

		public static Signature GetInstance(
			object  obj)
		{
			if (obj == null || obj is Signature)
			{
				return (Signature)obj;
			}

			if (obj is Asn1Sequence)
			{
				return new Signature((Asn1Sequence)obj);
			}

			throw new ArgumentException("unknown object in factory: " + obj.GetType().Name, "obj");
		}

		public Signature(
			AlgorithmIdentifier signatureAlgorithm,
			DerBitString        signatureValue)
			: this(signatureAlgorithm, signatureValue, null)
		{
		}

		public Signature(
			AlgorithmIdentifier	signatureAlgorithm,
			DerBitString		signatureValue,
			Asn1Sequence		certs)
		{
			if (signatureAlgorithm == null)
				throw new ArgumentException("signatureAlgorithm");
			if (signatureValue == null)
				throw new ArgumentException("signatureValue");

			this.signatureAlgorithm = signatureAlgorithm;
			this.signatureValue = signatureValue;
			this.certs = certs;
		}

		private Signature(
			Asn1Sequence seq)
		{
			signatureAlgorithm = AlgorithmIdentifier.GetInstance(seq[0]);
			signatureValue = (DerBitString)seq[1];

			if (seq.Count == 3)
			{
				certs = Asn1Sequence.GetInstance(
					(Asn1TaggedObject)seq[2], true);
			}
		}

		public AlgorithmIdentifier SignatureAlgorithm
		{
			get { return signatureAlgorithm; }
		}

		public DerBitString SignatureValue
		{
			get { return signatureValue; }
		}

		public Asn1Sequence Certs
		{
			get { return certs; }
		}

		/**
		 * Produce an object suitable for an Asn1OutputStream.
		 * <pre>
		 * Signature       ::=     Sequence {
		 *     signatureAlgorithm      AlgorithmIdentifier,
		 *     signature               BIT STRING,
		 *     certs               [0] EXPLICIT Sequence OF Certificate OPTIONAL}
		 * </pre>
		 */
		public override Asn1Object ToAsn1Object()
		{
			Asn1EncodableVector v = new Asn1EncodableVector(
				signatureAlgorithm, signatureValue);

			if (certs != null)
			{
				v.Add(new DerTaggedObject(true, 0, certs));
			}

			return new DerSequence(v);
		}
	}
}
